The 2030 decarbonisation level of 80% proposed in the letter was based on analysis contained in the Royal Society paper Beyond Dangerous Climate Change. The paper disaggregated global budgets to Annex 1 and non-Annex 1 nations; no direct reduction rates for the EU were calculated. In my letter to President Barroso I assumed the EU28 grouping was broadly representative of the Annex 1 group of nations. Building on this and the framing of the analysis outlined in the paper, I concluded that if the EU were to stand by its high-level statements on climate change it would need to deliver at least an 80% reduction in its emissions by 2030, not the 40% the Commission propose. The notes below provide the numbers underpinning the 80% conclusion, and are taken from Table 1 in the paper (for two global carbon budgets) combined with EU28 CO2 emission figures lifted from the Global Carbon Atlas

a) Based on a 1578GtCO2 global 2000-2100 carbon budget (~50% of exceeding 2°C)

Scenario C+5 proposes an 8% p.a. mitigation rate post a 2007 peak in Annex 1 emissions. For the EU28 this equates to a reduction from their 2007 emissions of 4007MtCO2 to 589MtCO2 by 2030; i.e. a reduction of 85% compared with 2007 (for 2000 and 1990 baselines the reduction level is within 1 percentage point of the 85% figure).

b) If the chance of exceeding 2°C was reduced to ~37% with an accompanying (and tighter) global budget of 1321GtCO2 for 2000-2100 then:

Scenario C+3 proposes a ~10.5% p.a. reduction post the 2007 Annex 1 peak, which would reduce the EU28 emissions to ~312MtCO2 by 2030. This relates to a reduction of around 92% on the EU’s 2007 emissions (similar levels of mitigation hold again for 2000 and 1990 baselines).

Ultimately, the letter adopts a conservative interpretation of such analyses (erring in favour of the EU) when it concludes if the EU was to abide by its own high level statements on climate change, it would need “an equitable and science-based 2030 decarbonisation target of around 80%. Anything less and the EU will renege on its 2°C commitments …”

NB: whilst the emission reductions outlined above for the EU (and Annex 1 nations) may be considered too demanding, they nevertheless are premised on a very challenging mitigation agenda for non-Annex 1 nations. The C+3 and C+5 scenarios both assume non-Annex 1 nations collectively peak emission by 2025 before reducing emissions rapidly at 7-8% p.a.